How do i paint trees on Custom Terrain/Ground from 3ds max?

Greeting people…
Im new to unity and i’m trying to do a real time architectural walk through here…

Initially, i just put my bungalow modeling on top of the unity terrain. My problem is that when i trying to punch/extrude a hole on the terrain for my pool beside a bungalow, it will affect and pull down other polygon that is unnecessary around the pool area as well…

My solution is to create my own terrain/ground in 3Ds Max and bring it into the scene…
So here is my question… how do i paint trees into my own custom made terrain/ground that came from 3Ds Max??? the only tree painting tool that i can find in unity is by using terrain from unity.

Or if back to my 1st problem… how do i punch/extrude a hole for my pool? the minimum unit for the brush size of terrain control is 1. which is 1meter as default. i cannot make the brush size goes any smaller than that.

You can’t actually paint trees on to a non-terrain object. However, you can still place trees, or you could write your own distribution script. Perhaps use a Perlin Noise texture, and place them randomly depending on the darkness of the noise? But you can’t just paint them on.

I needed to know the same thing and the answer that it isn’t possible doesn’t seem accurate. I wonder how many other tools like CTE (Custom Terrain Editor) & T4M are out there.

http://forum.unity3d.com/threads/cte-custom-terrain-editor-support-for-fbx-model-terrain-editing.161305/

http://www.azert2k.fr/T4M.html